GOOSE (Generic Object Oriented Substation Events) is a real-time network protocol for controlling devices via Ethernet networks. It is specified in the standard IEC 61850. GOOSE sends messages concerning the state of a device regularly at fixed intervals, for example every second. GOOSE messages are sent by multicast, i.e. a number of receivers can be informed simultaneously about the state of a sender.
A typical application of GOOSE is the spontaneous transmission of changes in state of energy automation components, such as for example the switch position (on/off) of switching devices, or other state messages of the energy automation component to further energy automation components. The energy automation components are connected to one another via Ethernet for exchanging the GOOSE messages. The advantage of controlling the energy automation components via Ethernet as compared with a conventional, direct device-to-device interconnection lies in the free configuration of the devices connected to the network. New cables do not have to be laid for new sending and receiving relationships. The proliferation of Ethernet and the possibility of using Ethernet for further services are reasons for using this technology.
GOOSE messages are accordingly transmitted on layer 2 of the OSI reference model. In this case, a GOOSE message sets the Ethertype field in an Ethernet data packet, whereby a prioritizing of the GOOSE message over other Ethernet messages is possible. The prioritizing has the effect that GOOSE messages are treated with preference over IP packets in the network, so that the delay within the network is as small as possible and the receiver receives GOOSE messages within a time window. This protocol structure allows the real-time capability of GOOSE.
Energy automation networks have a plurality of substations, each of the substations comprising at least one automation component as described above and a generally Ethernet-based communication network, via which the energy automation components can exchange messages according to GOOSE. For controlling the energy automation network, it is sometimes necessary that the state of an energy automation component of a substation is also transmitted to energy automation components in other substations. GOOSE in the original form generally cannot be used for this, since a public network connecting the communication networks (Ethernet) of the substations generally does not have multicast support or only offers this at relatively high costs. The public network, which is typically based on the Internet protocol, is generally a WAN (Wide Area Network), in which the data transmission takes place on layer 3 of the OSI reference model by using routing algorithms.
To be able nevertheless to transfer the transmission of GOOSE messages beyond the network limits of one substation into the communication network of another substation, the infrastructure of access nodes to the public network can be adapted. As a result, it is possible that also the public network can transmit messages on layer 2 of the OSI reference model. This may be realized for example as in the specification “IEC 61850 GOOSE over WiMax for fast isolation and restoration of faults in distribution networks”.
In IEC 61850-90-5, it is proposed to handle GOOSE messages via IP multicast and UDP. This is also known as “Routable GOOSE”.
A further alternative would be to set up layer-2 tunnels in the access nodes to the public network, that is to say the routers of the public network.
A disadvantage of the solution possibilities proposed above is on the one hand that modified hardware is required at the access points to the public network. On the other hand, the configuration of the individual energy automation components is laborious.